Reaction of polymeric materials with ethylene



Patented Feb. 20, 1951 REACTION OF POLYMERIC MATERIALS WITH ETHYLENEWilliam E. Hanford, Short Hills, N. J., and John R. Roland, Wilmington,Del., assignors to E. L du Pont de Nemours & Company, Wilmington, DeL, acorporation of Delaware No Drawing. Application April 16, 1947. SerialNo. 741,940

14 Claims.

This invention relates to processes for modifying polymers, It alsorelates to new polymeric products, and more specifically toethylene-modified polymers and their preparation. The new products ofthis invention are not to be confused with copolymers of ethylene,which, as has been disclosed heretofore, may be produced by a variety ofmethods unlike the method for preparing ethylene-modified polymershereinafter de scribed. The new products of this invention are preparedby treatment of pre-existing polymers, natural or synthetic, withethylene in the presence of a polymerization catalyst. This applicationis a continuation-in-part of our copending application S. N. 554,148,filed September 14, 1944, now abandoned.

An object of this invention is to provide a novel method for modifyingnatural and synthetic polymeric materials. Another object is to providea method for improving the moisture resistance,

and decreasing the water-absorbing tendency, of such polymers. A stillfurther object is to provide novel modified polymeric compositions having a wide variety of useful properties. Still other objects will appearhereinafter.

These objects are accomplished in accordance with the invention, byreacting natural or synthetic polymers with ethylene. Accordingly, theinvention comprises ethylene-modified polymers and a process formodifying natural and synthetic polymers by heating with ethylene underpressure in the presence of a free-radical producing compound as acatalyst. By free-radical producing compound" is meant that thecompound' is capable of generating free radicals un der the reactionconditions.

The products of this invention differ from copolymers, which containlinearly recurring units of all monomers used in their preparation. Thenew products contain chemically combined ethylene, and possessproperties difiering from those of the pie-existing polymer, frompolyethylene, and from a corresponding ethylene copolymer. Furthermore,the ethylene, after reaction in the presence of the pre-existingpolymer, cannot be separated therefrom by chemical or physical methods.

Inasmuch as ethylene is a gas at normal temperature and pressure, thisinvention requires suitable apparatus for gas phase reactions. Thisincludes means for compressing ethylene, pressure-resistant reactionvessels and means for heating and agitating such reaction vessels. Thepolymer to be modified may be submitted to ethylene treatment in blockform or better in thin films or fibers or still better in emulsion orsolution. In practicing one of the embodiments of this invention, asuitable reaction vessel is charged with an emulsion or solution of thepolymer and the polymer is thereafter treated with ethylene undercertain controlled conditions describcd below. This charging operationis usually con ducted under a blanket of deoxygenated nitrogen, or otherinert gas, to exclude oxygen. Alternatively, the solution or suspensionmay be added to an evacuated reaction vessel b means of a loading look.A. free-radical producing compound, which may be an organic or inorganicperoxide, or other compound as hereinafter dis closed, is included inthe reaction charge as a catalyst. The reaction vessel is then placed ina shaker machine provided with means for heating the vessel. Connectionis established with a high pressure source of ethylene, and appropriaterecording and controlling thermocouples are placed in position. Thevessel is pressured with ethylene and heating and agitation are started.The course of the reaction may be followed by the, pressure drop due toutilization of ethylene. The reaction rate is conveniently maintained bykeeping the ethylene pressure within a designated pressure range. Thisis accomplished by a periodic injection of fresh ethylene, or byperiodic injection of an inert solvent. The end of the reaction ismarked by the cessation of ethylene ab sorption, after which thereaction vessel is cooled, bled of excess ethylene, opened, and emptied.The modified polymer may be readil separated from the reaction mixtureby methods described in the following examples or by equivalents orsimple modifications thereof readily apparent to one skilled in the art.

The following examples illustrate the scope of the process of thisinvention, and demonstrate operable ranges of reaction variables. Thereaction vessel employed in these experiments is a 400 cc. pressureresistant vessel. All parts are given as parts by weight in c. g. s.units unless otherwise specified.

Example 1.A silver-lined high-pressure reaction vessel is charged withparts of a 33% emulsion of vinylidene chloride polymer, prepared asdescribed hereinafter, and 0.2 part of benzoyl peroxide. The pH of thismixture is 1.7. The vessel is placed in a heated shaker machine,pressured with ethylene, and heating and agitation are started. During areaction time of 10.5 hours throughout which the temperature ismaintained at 73 to 76 C. and the pressure at 880 to 1000 atmospheres,there is a total observed pressure drop of 125 atmospheres. The vesselis then cooled, opened, and the reaction mixture discharged. Thisreaction mixture is then treated with parts by volume of a 10% solutionof aluminum sulfate to coagulate the polymer. The polymer is filteredand washed with water until free ofemulsifier. The washed polymer isdried at 70 C. and there is obtained 20.9 parts of dry polymer. Thissoftens on a Blocl; Macquenne at 180 to 185 C. and contains 63.54%chlorine. From this it may be calculated that the ethylenemodifiedpolymer contains an average of 1 ethyleneunit for each 1.9 units ofvinylidene chloride. The polymer can be molded under pressure at 190 to200 C. with short heating cycles, whereas polyvinylidene chloride isextremely difilcult, if not impossible, to mold.

The emulsion of polyvinylidene chloride used in the above experiment isprepared as follows: A pressure vessel is charged with 125 parts ofoxygen-free water, 67 parts of vinylidene chloride, 11.4 parts of a 35%solution of a sodium salt of a secondary alkane sulfonic acid and 1 partof potassium persulfate. The vessel is purged of air by sweeping with astream of deoxygenated nitrogen, closed and placed in an agitating rackin a thermostat maintained at 50 C. The vessel and contents are thenheated for a period of 24 hours. A aliquot of the reaction mixture iscoagulated by the addition of a small amount of 10% aluminum sulfatesolution. The polymer is filtered, washed free of soap and dried. Thisyields 14 parts of polyvinylidene chloride and indicates completepolymerization of the vinylidene chloride.

Example 2.--A stainless steel-lined pressureresistant vessel is chargedwith a solution of 35 parts of cellulose acetate in 230 parts ofIA-dioxane and 0.2 part of benzoyl peroxide. The cellulose acetatecontains 53.43% of combined acetic acid. The vessel is closed, placed ina shaker machine, pressured with ethylene, and heating and agitation arestarted. During a reaction time of 16 hours, throughout which thepressure is maintained at 850 to 960 atmospheres and the temperature at79 to 83 0., there is a total observed pressure drop of 490 atmospheres.The vessel is then cooled, bled of excess ethylene, opened, and thecontents discharged. The reaction mixture is precipitated, by pouring asa thin stream, into two volumes of alcohol with vigorous stirring. Thepolymer thus obtained is filtered and dried. Thedried polymer is thenextracted with toluene in a continuous extractor. The soluble portion isan ethylene/dioxane wax which melts at 115 C. The insoluble portion isan ethylene-modified cellulose acetate which contains 52.5% of combinedacetic acid. By comparison with the original cellulose acetate whichcontained 53.43% combined acetic acid, it may be calculated that anaverage of 0.24 unit 'of ethylene combined with-each glucose unit of thecellulose acetate. Of this 0.04 mol of ethylene was positivelyidentified as ethoxy groups," for the polymer contained 0.63% ethoxyl byanalysis. The ethylene-modified cellulose acetate has a notably lowerwater absorption than the original cellulose acetate.

Example 3.-A stainless steel-lined pressureresistant vessel is chargedwith a solution of 41.8 parts of polyvinyl alcohol formal in 208 partsof 1,4-dioxane and 0.2 part of benzoyl peroxide. The vessel is thenclosed, pressured with ethylene and heating and agitation are started.During a reaction period of 16 hours, throughout which the temperatureis maintained at 78 to 86 C. and the pressure at 720 to 900 atmospheres,there is, a total observed pressure drop of 760 atmospheres. The vesselis then cooled, bled of excess ethylene, opened and the contentsdischarged. The polymer is precipitated by pouring into alcohol, dried,and extracted with toluene. The toluene-soluble portion, amounting to 35parts, is found to comprise an ethylene-modified polyvinylalcoholformal. This ethylene-modifled polymer contains 64.21% carbon and8.87% hydrogen, which corresponds to an empirical formula of Cad-11002.The original polyvinyl alcohol formal contained 53.06% carbon and 7.78%oxygen which corresponds to an empirical formula of C4.5H7.202. Thedifferences from whole numbers are attributable to the incompleteacetalization of the polyvinyl alcohol. The difference between theseempirical formulas is C1.9Ha.3. This indicates that an average of oneethylene reacted for each acetal unit of the polyvinyl alcohol formal.This ethylene-modifled polymer is found to be considerably moreresistant to organic solvents than the unmodified polyvinyl alcoholformal.

Example 4.-A stainless steel-lined, pressureresistant vessel is chargedwith parts of nonaethylene glycol and 0.3 part by volume of diethylperoxide. The vessel is closed, placed in a heated shaker machine,pressured with ethylene, and heating and agitation are started. During areaction time of 16.5 hours, throughout which the temperature ismaintained at 127 to 131 (3., except for a brief temperature surge to151 C.,

P and the pressure at 800 to 950 atmospheres there is a total observedpressure drop of 1115 atmospheres. The .vessel is then cooled, bled ofexcess gas, opened and discharged. The reaction mixture is poured into amixture of benzene and water to extract, respectively, theethylene-modified polyglycol, a surface active product, and theunreacted nonaethylene glycol. A portion of concurrently formed ethylenepolymer which does not dissolve in this mixture is filtered. The benzenelayer of the filtrate is separated, dried and evaporated. There is thusobtained 21 parts of an ethylene-modified nonaethylene glycol whichshows a high degree of surface activity in wetting sulfur and indeterging soiled fabrics. The water layer of the filtrate is evaporatedand there is thereby recovered 91.4 parts of nonaethylene glycol. Theethylene-modified nonaethylene glycol contains 79.47% carbon and 12.8%hydrogen. From this it may be calculated that the ethylene-modifiedproduct contains 18.6% by weight of ethylene and that on an average 3.16units of ethylene are combined with each molecule of nonaethyleneglycol.

Example 5.-A stainless steel-lined, pressureresistant vessel is chargedwith 0.2 part benzoyl peroxide and a solution of 35 parts of cellulosepropionate in 230 parts of 1,4-dioxane. The cellulose propionatecontains 59.79% combined propionic acid. The vessel is placed in aheated shaker machine, pressured with ethylene and heating and agitationare started. During a reaction time of 16 hours, throughout which thetemperature is maintained at 77 to 81 C. and the pressure at 750 to 965atmospheres, there is a total observed pressure drop of over 1000atmospheres. The reaction is very vigorous and momentary temperaturesurges to as high as C. are observed. The vessel is then cooled, bled ofexcess ethylene, opened and the reaction mixture discharged. The solidproduct is precipitated by pouring into methanol after which it isfiltered and dried. The solid product is then extracted with boilingbenzene to separate 14 parts of ethylene/dioxane wax. The insolublepolymer is found to comprise 30 parts of an ethylene-modified cellulosepropionate. This contains 21.96% combined propionic acid. From thisanalysis and that of the original cellulose propionate it may becalculated that an average of 18.1 units of ethylene are combined witheach glucose unit of the cellulose propionate. This modified cellulosepropionate is found to be in soluble in cold acetone, xylene,acetone-xylene (50-50 by volume), ethanol, ethanol-xylene, (50 50 byvolume), tetrachloroethylene, ethyl acetate, chloroform, dioxane, anddioxane-xylene (50- 50 by volume). The ethylene-modified cellu losepropionate is also substantially insoluble in these solvents at 80 C.Slight swelling, but no true dissolution, is observed in hot xylene. Theoriginal cellulose propionate is very sensitive to similar solvents inthat it is either soluble in or highly swollen by them.

Similar treatment of ethyl cellulose effects a combination of about 1unit of ethylene for each glucose unit of the ethyl cellulose.

Example 6.A stainless steel-lined pressureresistant vessel is chargedwith 100 parts of water, 0.2 part of benzoyl peroxide and a 6" x 12"film of methyl acrylate polymer, (about 7 parts). The film is supportedon a rack in such a fashion as to prevent sagging and me chanical damageand to provide intimate contact with the remainder of the reactionmixture. The vessel is then closed, evacuated to remove air, placed in aheated shaker machine, pressured with ethylene and heating and agitationare started. During a reaction time of 8 hours,

tached to the polyamide.

throughout which the temperature is maintained at 72 to 82 C. and thepressure to 850 to 960 atmospheres, there is a total observed pressuredrop of 430 atmospheres. The vessel is then cooled, bled of excessethylene, opened and the contents discharged. The reaction mixture isfiltered and dried. The film of methyl acrylate polymer is covered withethylene polymer. These are separated by dissolution of the former inboiling acetone in which solvent neither polyethylene norethylene/methyl acrylate copolymer is soluble. found to contain 57.6%carbon and 7.55% hydrogen from which it may be calculated that thepolymer contains an average of 1 unit of ethylene combined for each 5units of the methyl acrylate. This ethylene-modified polymer is stifferthan methyl acrylate polymer and has a lower water absorption.

Example 7.A stainless steel-lined pressureresistant vessel is chargedwith 100 parts of tertiary butyl alcohol, 20 parts of polyvinyl acetate(2. commercial grade having a saponification number of .653) and 0.3part'by volume of diethyl peroxide. The vessel is closed, evacuated toremove air, placed in a heated shaker machine, pressured with ethylene,and heating and agitation are started. During a reaction time of 7.75hours, throughout which the temperature is maintained at 128 to 137 C,and the pressure at 750 to 1000 atmospheres, except for a brief periodof rapid reaction when it dropped to 550 atmospheres, there is a totalobserved pressure drop sf 1500 atmospheres. The vessel is then cooled,bled of excess ethylene, opened and the contents discharged. Thetertiary butyl alcohol is separated from the reaction mixture by evapo-Thi ethylene-modified polymer is ration in vacuum on a. steam bath, andthe solid residue is then extracted with alcohol and with toluene. Theethylene-modified polyvinyl acetate is obtained from these extracts byevaporation of the solvent. The alcohol extracted polymer is found tohave a saponificatio'n number of 455.9. Compared with thesaponiification number of the original polyvinyl acetate of 653, theseanalyses show that an average of 1.4 units of ethylene combined witheach vinyl acetate unit of the polymer.

Example 8.--A synthetic linear polyamide is prepared by reacting 35.5parts of hexamethylenediammonium adipate, 26.5 parts ofhexamethylenediammonium sebacate and 38 parts of caprolactam, asdisclosed in U. S. Patent 2,285,- 009. Two hundred parts of a 15%solution of this polyamide in methanol-water (/20 ratio by volume) and0.5 part of benzoyl peroxide dissolved in 13.2 parts of pure benzene arecharged into an autoclave. The autoclave is flushed with oxygen-freenitrogen and pressured with ethylene. The autoclave is heated to 80 C.and the pressure adjusted to between 800 and 900 atmospheres withethylene, where it is maintained for 10.5 hours. During this periodthere is an observed pressure drop corresponding to 515 atmospheres ofethylene. On cooling, the reactor is opened and the product is removedas a white gel which is washed with acetone in a Waring Blendor. Theproduct is then filtered and dried to give 51 parts of a white powder. Aportion of this powder, amounting to 35.5 parts, is extracted in aSoxhlet apparatus for 72 hours with boiling toluene in order to removeany polyethylene that has not become chemically at- The residue amountsto 25 parts and analysis shows that it corresponds to a productcontaining 28.5% of ethylene. The residue from the extraction isinsoluble in boiling toluene which is a solvent for polyethylene andmethanol-water mixtures which dissolve the polyamide. A hot pressed filmof the modified polyamide is found to be more impermeable to the passageof water vapor than are control films of polyethylene and polyamide. Theproperties of the modified polyamide film in comparison with unmodifiedpolyethylene and unmodified polyamide are tabulated below:

P C t watcrblqapog lcr- Per Cent Tensile er Modulus 1 Elongaof Water/sq. Ethylene lb./1n. tion lbjm. meters of mi! u film/hour Example 9.Twohundred parts of a 15% solution of the polyamide of Example 8 inmethanolwater (80-20 by volume) and 0.2 part of ditertiary butylperoxide in 8 parts of methanol are charged into an autoclave. Theautoclave is heated to 120 C. and pressured to between 800 and 900atmospheres with ethylene. The pressure is maintained in this range for10 hours. During this period there is a total observed pressure drop of1040 atmospheres of ethylene. After this period of reaction theautoclave is allowed to cool and the contents discharged. The product, awhite spongy gel, is washed with acetone in a Waring Blendor, leaving 80parts of a. fine white powder. A portion of this powder, amountbY1i%iPer Cent mea y at Per Cent Tensile, Modulus, or water 1008 Ethylenelb./in.= 3 ,235 lb.lin. meters film/hour Example 10.'A synthetic linearpolyamide is prepared by reacting 35.5 parts of hexamethylenediammoniumadipate, 26.5 parts of hexamethylenediammonium'sebacate and 38 parts ofcaprolactam, as disclosed in U. S. 2,285,009. Onehundred parts of a 5%solution of this polyamide in methanol-water (80-20 by volume) and 0.2part of di-t-butyl peroxide dissolved in 64 parts of methanol and partsof water are charged into an autoclave. Theautoclave is flushed withoxygen free nitrogen and pressured with ethylene. The autoclave isheated to 120 C. and the pressure, adjusted to between 800-900atmospheres with ethylene where it is maintained for 9 hours. Duringthis period there is an observed pressure drop corresponding to 1,290atmospheres of ethylene. On opening the autoclave there is found a gooddispersion of polymer which shows some thixotropic properties. Theparticles of dispersed polymer appear perfectly spherical in shape underthe microscope and for the most part are 2-3 microns in diameter. Thedispersion contained 29.1% total polymer.

In the practice of this invention there may be used any linear polymerwhether natural or synthetic. Examples of natural and modified naturalpolymers that may be employed are cellulose, silk, wool, and celluloseesters and ethers, e. g., nitrocellulose, cellulose acetate, cellulosepropionate, methyl cellulose, ethyl cellulose, and cellu lose glycolate.The synthetic polymers are those obtainable either by additionpolymerization or by condensation polymerization. Of the syntheticpolymers, it is.- preferred to use those which contain halogen orcertain oxygenated groups, preferably ester, amide, 0r acetal'groups.These groups may be lateral to the polymer chain, as in polyvinylchloride, polyvinyl acetate, or integral therewith as in the polyestersand polyamides formed by condensation polymerization.

Examples of addition polymers are those obtainable from vinyl andvinylidene compounds.

There are numerous substances of this type, and by way of example thosewhich can be used in the practice of this invention include vinyl esterpolymers (polyvinyl chloride, polyvinyl fluoride, polyvinyl bromide,polyvinyl acetate, and the like), polyvinylidene chloride,polyvinylidene fluoride, polyvinyl ethers, e. g., poly (methyl vinylether), etc., polymers of l-chloro-l-fluoroethylene, vinylchloride/vinyl carboxylate polymers, i. e., vinyl chloride/vinyl acetatepolymers, alkyl polyacrylates and polyalkacrylates, etc.

Examples of linear condensation polymers that can be used are thesynthetic linear polyamides, polyesters, polyesteramides, polyacetals,polyethers and polyanhydrldes, of the general types described in U. S.Patent 2,071,250. Of these synthetic linear condensation polymers thepolyamides are especially suitable. These are defined in U. 8. 2,359,877and are made as disclosed in U. S. Patents 2,071,253 and 2,130,948 bymethods which comprise self-polymerization of a monoaminomonocarboxylicacid and by reaction of essentially equimolar amounts of a dibasic acidwith a diamine. Examples of such polyamides are polymerized aminocaproicacid, polyhexamethyleneadipamide and polyhexamethylenesebacamide.Polyamides containing heteroatoms as described in U. S. Patents2,158,064 and 2,191,556 can also be used. The interpolyamides because oftheir good solubility characteristics, represent a valuable class ofsynthetic linear condensation polymersfor use in the practice of thisinvention. Such interpolyamides are obtained by reacting together aplurality of polyamide-forming compositions, e. g., as described in U.S. Patents 2,252,554 and 2,252,555. An especially suitable.interpolyamide because of its excellent solubility characteristics isthat obtained by reacting together about of hexamethylenediammoniumadipate, 30% hexamethylenediammonium sebacate and 30% omega-aminocaproicacid as described in U. S. Patent 2,285,009.

The polyester-amides used in the practice of this invention are the highmolecular weight linear condensation polymers described in U. S. Patents2,071,250, 2,224,037 and 2,312,879. These polyester-amides are preparedfor example, by reacting an omega-hydroxy acid with a diamine and adibasic acid, 'by reacting an aminoalcohol with a dibasic acid, byreacting a glycol with a diamine and a dibasic acid, or by reacting aglycol with an aminoacid and a dibasic acid.

The polyesters used' in the practice of this invention are the highmolecular weight polymers described in U. S. Patent 2,071,250 and whichare made by self-esterification of hydroxy acids, such asomega-hydroxydecanoic acid, or by reaction of a dibasic acid, e. g.,suberic acid, with. a di-' hydric alcohol, e. g., trimethylene glycol.

Still further types of polymers useful in the practice of this inventionare the polyethers,

polyanhydrides, and polyacetals described in the above-mentioned U. S.Patent 2,071,250 and the polyacetals described in U. S. Patent2,071,252.

Examples of modified preformed synthetic polymers useful in the practiceof this invention are the N-alkoxymethyl polyamides obtained by reactingat moderate temperature (25 to 75 C.) .a formic acid solution of apolyamide with alcohol and formaldehyde, or by other methods describedin the copending application of T. L. Cairns, Serial No. 539,195, filedJune 7, 1944, now Patent No. 2,430,860, November 18, 1947, chlorinatedpolyethylenes such as disclosed in U. S. Patent 2,183,556 and thedehalogenated polyethylenes disclosed in U. S. Patent 2,261,757,polyvinyl formals, acetals, and butyrals formed by reacting eitherpolyvinyl alcohol or a partially hydrolyzed polyvinyl ester with analdehyde, e. g.,

or attached laterally to, the polymeric chain are also satisfactory.

The ethylene to be used in the practice of this invention should berelatively pure and it is usually desirable to have it free of oxygenand acetylene at least to the extent of not more than 1000 parts permillion, generally to less than 500 parts per million and preferably toless than 100 parts per million. These very small amounts of oxygen maybe catalytically active, especially in the absence of otherpolymerization catalysts. Thus, the ethylene should preferably besubjected to deoxygenation pretreatment, which, if desired, may be inaccordance with the method described in U. S. Patent 2,351,167. Theethylene may contain small amounts of other contaminants which appear tobe less deleterious for the reaction. These include, in smallconcentrations, carbon dioxide, carbon monoxide, propylene, propane,hydrogen and nitrogen. Ethylene from any commercial source may be usedin the practice of this invention and since such ethylene usuallycontains contaminants it should be freed of such substances. Forexample, acetylene may be removed by absorption in a solvent, throughthe use of a scrubbing tower.

The temperature used in the practice of this invention usually is withinthe range of from about 30 to 400 C. The thermal degradation of polymersis often quite rapid but, in the practice of this invention thedegradation appears to be completely eliminated or much minimized byconducting the heating in an atmosphere of ethylene. Although thisdegradation is much minimized even at the higher temperature ranges, itis usually preferred to conduct the process of the invention in the morerestricted temperature range of 50 to 250 C. The actual temperature tobe employed is dependent on the type of catalyst, and as notedhereinafter, on the chosen pressure range. Thus the organic andinorganic peroxy compounds, i. e., compounds containing the O--O--group, are generally used in the temperature range from 50 to 150 C.;the oximes are generally operable at 100 to 225 C., and the hydrazinecompounds, per halo compounds, azines, and positive halogen compounds at150 to 300 C., preferably 200 to 300 C. As noted above, oxygen, in smallconcentrations, is a catalyst for the reaction, suitabe temperaturesbeing 200 to 300 0., preferably 200 to 250 C. These temperature rangesfor the several classes of catalysts are for batch operation, and whenthe process is carried out in a continuous manner minor alterations,dependent on the contact time, are necessary. This correction usuallyrequires a revision upwards from the limits given by about 25 to 50 C.

The process of this invention may be practiced at any ethylene pressureabove atmospheric. However, at low pressures the ethylene concentrationis quite low and the process is generally practiced at ethylene pressurefrom 50 to 1500 atmospheres and preferably at 500 to 1500 atmospheres,for largely by this means is a practicatly high ethylene concentrationmaintained. For preparin very highly modified polymers and for attaininghigh reaction rates even higher ethylene pressures, up to 3000atmospheres, may

be used. The temperatures and pressures used in the practice of thisinvention are interdependent variables and either must be determinedwith respect with respect to the other. For example, if low pressuresare elected, relatively high temperatures are required. Conversely theuse of high- Ill) 10 er pressures permits the employment of relativelylow temperatures. Appropriate temperature-pressure combinations can betaken from the specific examples given or by simple modification thereofto effect different ratios of ethylene reacting or to obtain differentreaction rates.

The modification of pre-exlsting polymers with ethylene may be conductedin any suitable reaction medium. For example, the reaction may beconducted with a solution of the polymer or with a dispersion of thepolymer or with. bulk forms of the polymer, preferably with thin formssuch as films and fibers. The reaction medium may thus comprise anyorganic material which is a good solvent for the polymer or may comprisewater with any of the well known dispersing or modifying agents, such assoaps, sodium alkyl sulfates, sodium alkanesulfonates, long chainammonium salts, long chain betaines, and the like.

The free radical producing substances. which may be used in the practice01' this invention, include the peroxy compounds, 1. e., compounds whichcontain the --O--O- grouping, e. g., diacyl peroxides such as diacetylperoxide, bibutyryl peroxide, dipropionyl peroxide, dilauroyl peroxide,dioleyl peroxide, dibenzoyl peroxide, benzoyl acetyl perox de, anddialkyl peroxides such as dimethyl, diethyl, dipropyl, diisopropyl anddibutyl peroxides or per salts such as ammonium and alkali metalpersulfates, perborates and percarbonates, etc. Other free radicalforming substances which may be used include the azines, e. g.,benzalazine, diphenylketazine, etc., hydrazines, e. g., hydrazinehydrochloride, dibenzoyl hydrazine, etc., oximes, e. g., acetoxime,camphoroxime, butyraldoxime, etc., amine oxides, e. g. trimethylamineoxide, etc., perhalo compounds, e. g., hexachloroethane andoctachloropropane, etc., positive halogen compounds, e. g., sodioN-chloro-p-toluenesulfonamide, sodio N- chlorobenzene-sulfoneamide,1,3-dichloro-5,5-dimethylhydantoin, etc. These catalysts do not catalyzethe Friedel-Crafts reaction. The preferred catalysts are the peroxycompounds because they are active at low concentrations and do notrequire the use of excessively high temperatures. Friedel-Crafts typecatalysts are not suitable in the practice of this invention.

The modified polymers prepared in accordance with this invention arecharacterized in that they contain ethylene units attached to thepre-existing polymeric chain. This is shown by analysis of the modifiedpolymers, as illustrated in the examples. The mechanism of the reactionwhereby such a result is obtained is not known with certainty, but it isbelieved to involve formation of a free radical from the pre-existingpolymer, thus providing a point Wherefrom a new polymer chain can grow.Regardless of the mechanism it is evident that the modified linearpolymers in general contain substituent ethylene and/or polyethylenegroups. In some instances such substituent groups may serve tocross-link two or more of the original polymer molecules.

It is usually desirable that the portions of the reactor in immediatecontact with the reaction mixture be of materials which do not rapidlycatalyze the decomposition of the peroxides or induce side reactions ofthe catalyst. Suitable examples of such materials include silver,stainless steels, aluminum, tin, lead, glass, and enamel. Ordinary teelis often found to be unsuitable unless it has been conditioned bypickling with dilute peroxide solutions, by conducting a per- 11oxide-catalyzed reaction therein, or sometime by highly polishing thesurfaces to a mirror finish.

When the process of this invention involves a reaction of aheterogeneous system it is desirable to maintain all reactants inintimate contact by agitation. The agitation may be applied in anymanner, for example, by vigorous stirring, by turbulent flow'in atubular reactor, by efllcient bubbling of the gas phase through theliquid phase, or by any other means which will accomplish this end.

Although the illustrative examples given above relate to a batchoperation, the process may also be conducted in a continuous manner.Continuous operation provides for great ease of temperature control. Theethylene reactions of this invention are highly exothermic, and whenrelatively small masses'of reactants are processed per unit of space inthe reaction system, relatively small quantities of heat are evolved.This improved temperature control minimizes degra= dation of thepre-existing polymer and makes for more accurate control of the degreeof modification by ethylene. Furthermore, the high space= time yield ofa continuous unit makes the process more economical because of therelatively small capital investment involved, and also because ofelimination of "stand-by time for cleaning, unloading and other suchoperations.

The term polymer as used in the description and claims refers tomacromolecular materials having a plurality of recurring units.

We claim:

1. A process for modification of cellulose esters which comprisesheating a cellulose ester in a solvent with ethylene under a pressurewithin the range of about 750 to 965 atmospheres at a temperature in therange of about 50 to 150 C. in the presence of a catalytic amount of afree radical producing compound, whereby an ethylenemodified celluloseester, characterized by decreased compatibility with organic solvents,is obtained.

2. A process for modification of vinyl ester polymers which comprisesheating a pre-existing vinyl ester macromolecular polymer in a solventwith ethylene under a pressure withinthe range of about 550 to 1000atmospheres at a temperature of about 50 to 150 C. in the presence of acatalytic amount of a free radical producing compound, whereby anethylene-modified vinyl ester macromolecular polymer, having a lowersaponification value than the unmodified polyvinyl ester is obtained.

3. A process for modification of a synthetic linear polyamide havingrecurring carbonamide groups as an integral part of the main polymerchain which comprises heating a synthetic macromolecular linearpolyamide with ethylene under a pressure of about 500 to 1500atmospheres at a temperature of about 50 to 150 C. in the presence of acatalytic amount of a peroxy compound whereby an ethylene-modifiedsynthetic linear polyamide is obtained.

4. The product obtained in accordance with the process which comprisessubjecting a cellulose ester to reaction with ethylene at a temperaturewithin the range of about to 400? C. under a pressure of from 1 to 3000atmospheres in the 5. The product obtained in accordance with theprocess which comprises subjecting a synthetic macromolecular linearpolyamide having recurring carbonamide groups as an integral part of themain polymer chain to reaction with ethylene at a temperature within therange of about 30 to 400 C. under a pressure of from 1 to 3000atmospheres in the presence of a catalytic quantity of free radicalproducing compound, whereby ethylene becomes chemically combined withthe said synthetic linear polyamide and thereafter separating themodified synthetic linear polyamide from the resultant mixture.

6. The product obtained in accordance with the process which comprisessubjecting a vinyl ester macromolecular polymer to reaction withethylene at a temperature within the range-of about 30.to 400 C. under apressure of from 1 to 3000 atmospheres in the presence of a catalyticquantity of free radical producing compound, whereby ethylene becomeschemically combined with the said vinyl ester macromolecular polymer andthereafter separating the modified vinyl ester macromolecular polymerfrom the resultant mixture.

7. A process for the modification of pre-existing macromolecularpolymeric materials which comprises subjecting a pre-existing polymericmaterial of the class consisting of linear polymeric esters, linearpolymeric ethers, linear halogenated hydrocarbon polymers and linearpolyamides having recurring carbonamide groups as an integral part ofthe main polymer chain to reaction with ethylene under superatmosphericpressure in the presence of a catalytic quantity of a free radicalproducing compound as a catalyst whereby ethylene becomes chemicallycombined with the said pre-existing polymer.

8. A process for the preparation of ethylenemodifled polymers whichcomprises subjecting a pre-existing macromolecular polymeric material ofthe class consisting of linear polymeric esters. linear polymericethers, linear halogenated hydrocarbon polymers and linear polyamideshaving recurring carbonamide groups as an integral part of the mainpolymer chain to reaction with ethylene at a temperature within therange of about 30 to 400 C. under a pressure of from 1 to 3000atmospheres in the presence of a catalytic quantity of free radicalproducing compound, whereby ethylene become chemically combined with thesaid pre-existing polymer.

9. A process for the modification of polymeric materials which comprisesheating a pro-existing macromolecular polymeric material of the classconsisting of linear polymeric esters, linear polymeric ethers, linearhalogenated hydrocarbon polymers and synthetic linear polyamides havingrecurring carbonamide groups as an integral part of the main polymerchain with ethylene at a temperature within the range of about 50 to 250C. under a pressure of about 500 to 1500 atmospheres in the presence ofa catalytic quantity of a free radical producing compound, wherebyethylene units become attached to the preexisting polymeric material.

10. A process for the modification of polymeric materials whichcomprises heating a macromolecular polymeric material of the classconsisting of linear polymeric esters, linear polymeric ethers, linearhalogenated hydrocarbon polymers and synthetic linear polyamideshaving-recurring carbonamide groups as an integral part of the mainpolymer chain with ethylene containing less than 1000 parts per millionof oxygen at a temperature within the range of 50 to 250 C. under apressure within the range 01' 500 to 1500 atmospheres in the presence ofa catalytic quantity of a free radical producing compound wherebyethylene units become attached to the preexisting polymeric material.

11. The process set forth in claim 10 in which the said pre-existingpolymeric material is a cellulose ester.

12. The process set forth in claim 10, in which the said pre-existingpolymeric material is a synthetic linear polyamide having recurringcarbonamide groups as an integral part of the main polymer chain.

15 13. The process set forth in claim 10, in which the pre-exlstingpolymeric material is a vinyl ester polymer.

14. An organic polymeric material modified by forming an integral partthereof, said modified polymer being obtained by the process of claim10.

WILLIAM E. HANFORD. JOHN R. ROLAND.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS OTHER REFERENCES Russell et al., pp. 183-189, Ind.and Eng. Chem.,

polyethylene chain chemically bound thereto and 20 Feb. 1938.

7. A PROCESS FOR THE MODIFICATION OF PRE-EXISTING MACROMOLECULAR POLYMERIC MATERIALS WHICH COMPRISES SUBJECTING A PRE-EXISTING POLYMERIC MATERIAL OF THE CLASS CONSISTING OF LINEAR POLYMERIC ESTERS, LINEAR POLYMERIC ETHERS, LINEAR HALOGENATED HYDROCARBON POLYMERS AND LINEAR POLYAMIDES HAVING RECURRING CARBONAMIDE GROUPS AS AN INTEGRAL PART OF THE MAIN POLYMER CHAIN TO REACTION WITH ETHYLENE UNDER SUPERATMOSPHERIC PRESSURE IN THE PRESENCE OF A CATALYTIC QUANTITY OF A FREE RADICAL PRODUCING COMPOUND AS A CATALYST WHEREBY ETHYLENE BECOMES CHEMICALLY COMBINED WITH THE SAID PRE-EXISTING POLYMER. 